1. Field of the Invention
The present invention relates to the field of liquid crystal display techniques, and in particular to an LED backlight driving circuit, a backlight module, and a liquid crystal display device.
2. The Related Arts
The backlight driving circuit of the light emitting diode (LED) provided in the prior art is shown in FIG. 1. When the driving signal is high, the metal-oxide-semiconductor field-effect transistor (MOSFET) is on, and the inductor current increases, which stores the energy. When the driving signal is low, the MOSFET is off, and the inductor generates the reverse induced electromotive force, which is connected in series with the input voltage 24V, and releasing the energy to the LED strings. At this time, the positive electrode voltage of the LED strings is very high, which is Vo=24/(1−D), where D is the duty cycle of the driving signal. If the number of each LED strings is 10, Vo is 60˜70V generally, this high voltage exceeds the human safety voltage 36V.
Therefore, the LED backlight driving circuit provided in the prior art has the following disadvantages.
The output voltage of the LED backlight driving circuit is higher, if someone touches the circuit while it is operating, he will get hurt; when the LED backlight driving circuit is operating abnormal, it is possible to find out where the problem is by measuring the voltage and the current of each circuits one-by-one through the oscilloscope. The circuit board is still under the input power of 24V in this process, it may appear unpredictable security risks during the debugging process, and the working efficiency will also be reduced.